The field of the invention relates to a concrete cure which forms a relatively water impermeable barrier to retard the loss of water from the concrete mix during the early hardening period.
Conventional concrete curing formulations comprise waxes and/or resins dissolved in modified solvents. While such cures successfully achieve prescribed water retardation specifications, problems with the solvents have created the need for a water based cure. Some of the inherent difficulties with solvent based cures include environmental and pollution concerns, clean-up for the contractor and flammability.
Latex based cures have also been used, but they fail to set up quickly enough to retard early moisture release from the concrete to the atmosphere. In this type cure, the latex is a liquid monomer that is dispersed in liquid and then polymerized.
Other cures have utilized resin solvents with water, but the water was the interior, or discontinuous, phase and did not provide a truly water based formulation wherein the water itself was the exterior, or continuous, phase.
A limitation in the atmospheric dispersion of resins has required that the melting point be near 100.degree. C. because of the difficulty in achieving dispersion in water below its boiling point. Resins with lower melting points have been known to leave tacky films when dry.
Providing a water based cure is highly desirable because by being water reducible it allows the contractor an easy clean-up.
Environmental considerations are also a factor and it would be additionally beneficial to eliminate organic solvents to reduce pollution.
As found with other attempts employing resins, exposure to ultraviolet light can cause discoloration.
While existing solvent based cures satisfy moisture retention requirements, it has been difficult to provide a water based formulation meeting these specifications as well.
From an economic standpoint it would be desirable to eliminate the need for more costly solvents and utilize water at a much lower cost.
An added benefit to the use of a water based cure is that the flammability hazard, inherent with solvent based cures, can be eliminated.
Accordingly, it is a primary goal of the invention to provide a concrete cure that is totally water based and completely void of solvents.
An important object of the invention is to provide a resin/wax single phase dispersion that meets design criteria, which has not been made possible heretofore.
It is a further goal of the invention to provide a water based cure which can be applied to fresh concrete and retain over 95% of the mixing water for a minimum of 72 hours which applied at the rate of 200 ft.sup.2 /gallon (5 m.sup.2 /dm.sup.3).
It is an allied objective of the invention to satisfy environmental protection needs by omitting the use of solvents.
It is further a goal of the invention to provide a water based concrete cure which has the correct viscosity to make it capable of being sprayed with conventional applicator nozzles.
It is a concomitant object of the invention to provide a cure which may be exposed to ultraviolet light without discoloration.
It is further an object of the invention to eliminate the hazards of flammability.
It is another object of the invention to provide a water based cure which may be provided in a clear or pigmented formulation which meets state and federal specifications.
The water based concrete cure of the invention satisfies these foregoing goals and needs. The cure may be summarized in one form as having a mixture of hydrocarbon resin, emulsifying agents, paraffinic wax, and a minimum water content of about 60% by weight to yield a sprayable viscosity.
A method for the preparation of a water based cure is provided which includes the steps of melting a hydrocarbon resin and paraffinic wax. The molten resin/wax is then dispersed in water with a suitable emulsifying agent. Additional water is subsequently added to reduce solids and achieve a desired viscosity. The system is then agitated to ensure thorough mixing. The cure may then be containerized for shipment or applied to concrete.
The invention further provides a method for the preparation of a pigmented cure in which a predispersed pigment is added to the emulsified resin/wax in water. The predispersion steps include first adding water to a vessel, followed by the addition of an emulsifying agent. Then, the pigment is added to the vessel and dispersed. A small amount of additional water may be added to this first vessel to reduce the viscosity and reach a desired pumpable consistency. The predispersed mixture is then pumped to a second vessel for mixing with the emulsified resin/wax and water to thereby provide a pigmented concrete cure.